1. Field of the Invention
The present invention relates to electronic image forming apparatus and more particularly, to a supporting apparatus for a photosensitive drum, which has a high precision and high strength structure for supporting a photosensitive drum on a toner cartridge.
2. Description of the Related Art
A regular electronic image forming apparatus such as copier or printer generally has a cylindrical photosensitive drum mounted in a toner cartridge. During installation, two shaft members are fastened to the two opposite ends of the photosensitive drum, and then the photosensitive drum is mounted in the housing of the toner cartridge as designed and supported between two end caps in the housing of the toner cartridge. The end caps each have a coupling tube for receiving the shaft members respectively, allowing rotation of the photosensitive drum around the shaft members.
The aforesaid two end caps are bonded to the housing of the toner cartridge by ultrasonic welding, not detachable. When replacing the photosensitive drum, at least one shaft member must be broken. When installing a new photosensitive drum, as shown in FIG. 1, a sleeve member 2 which has an axial hole 3 and four longitudinal locating grooves 4 equiangularly spaced around the axial hole 3 is fastened to one end of the photosensitive drum 1, and then the photosensitive drum 1 with the sleeve member 2 are inserted into the housing of the toner cartridge (not shown), and then an shaft member 5 is inserted into the axial hole 3 to support the photosensitive drum on a coupling tube at one end cap in the housing of the toner cartridge. The shaft member 5 has four longitudinal locating ribs 7 respectively engaged with the four longitudinal locating grooves 4 of the sleeve member 2 and four hooks 6 hooked on one end edge of the sleeve member 2. Therefore, the sleeve member 2 is firmly connected with the shaft member 5 for synchronous rotation with the shaft member 5.
The aforesaid sleeve member 2 and shaft member 5 are respectively molded from plastics. Because the shaft member 5 has four longitudinal ribs 7 and the sleeve member 2 has four longitudinal grooves 4, the sleeve member 2 and shaft member 5 may not have a superior concentricity due to existing mold stripping technical problem, resulting in eccentric rotation of the photosensitive drum. Further, because the sleeve member 2 is shaped like a round tube, it has a low structural strength and tends to be deformed. Deformation of the sleeve member 2 will also affect the rotation action of the photosensitive drum.